In a previously known disc filter of this kind (SE-C-7406315-7) the axial suction channels are connected with the radially inner portions of the filter elements. Particularly when filtering pulp suspensions, the suction channels axially extending between the discs constitute an obstacle for falling lumps of the filter cakes deposited on the filter elements, so that such lumps can even end up hanging over the suction channels.
This problem was addressed in Swiss Patent No. 162,137 by providing peripheral suction and a central discharge funnel for filter cake. However, this construction gave rise to the further problem of backflow of the liquid radially inwardly when the filter elements rise above the liquid surface.